gistfile1.rb

  def self.by_growth(start, stop=Time.now)
    votes = Vote.arel_table
    select("`photos`.*, COALESCE(SUM(`votes`.value),0.0) AS score_diff")
      .joins(:votes)
      .where(votes[:created_at].gt(start), votes[:created_at].lt(stop))
      .group(votes[:photo_id])
      .order("score_diff DESC,score DESC")
  end